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Federal Register / Vol. 86, No. 138 / Thursday, July 22, 2021 / Proposed Rules PART 39AIRWORTHINESS
DIRECTIVES
1. The authority citation for part 39
continues to read as follows:

Authority: 49 U.S.C. 106g, 40113, 44701.
39.13

Amended
2. The FAA amends 39.13 by adding the following new airworthiness directive:

Airbus Helicopters: Docket No. FAA2021
0197; Project Identifier 2018SW107
AD.
a Comments Due Date The FAA must receive comments on this airworthiness directive AD by September 7, 2021.
b Affected ADs None.
c Applicability This AD applies to Airbus Helicopters Model EC 155B and EC155B1 helicopters, certificated in any category.
d Subject Joint Aircraft Service Component JASC
Code: 6300, Main Rotor Drive System.
e Unsafe Condition This AD defines the unsafe condition as failure of a main gearbox MGB planet gear assembly. This condition could result in failure of the MGB and subsequent loss of helicopter control.
f Compliance Comply with this AD within the compliance times specified, unless already done.

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g Required Actions 1 For helicopters with at least one Type Y planet gear assembly with a serial number S/N listed in Appendix 4.A. of Airbus Helicopters Alert Service Bulletin ASB No.
EC15505A034, Revision 5, dated December 4, 2018 ASB EC15505A034 Rev 5 or with at least one Type Z planet gear assembly with an S/N listed in Appendix 4.B. of ASB
EC15505A034 Rev 5 installed, within 10
hours time-in-service TIS after the effective date of this AD, and thereafter at intervals not to exceed 10 hours TIS, inspect the MGB
magnetic plugs for particles. If there are any particles that consist of any scale, flake, splinter, or other particle other than cotter pin fragments, pieces of lock wire, swarf, abrasion, or miscellaneous non-metallic waste, and any of the planet gears have accumulated less than 50 total hours TIS, before further flight, inspect the MGB filter and oil sump for particles. Thereafter, for 25

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hours TIS, continue to inspect the MGB plugs for particles before each flight, inspect the MGB filter and oil sump for particles at intervals not to exceed 25 hours TIS, and inspect the cumulative surface area of the particles collected from the magnetic plugs, the MGB filter, and the oil sump, since last MGB overhaul, or since new if no overhaul has been performed.
Note to paragraph g1: Airbus Helicopters service information refers to an MGB filter as an oil filter.
i If the total surface area of the particles is less than 3 mm2, examine the particles with the largest surface area S, greatest length L, and greatest thickness e.
A If any S of all of the particles is less than or equal to 1 mm2, the L is less than or equal to 1.5 mm, and the e is less than or equal to 0.2 mm, inspect the MGB plugs for particles before further flight, and inspect the MGB filter and oil sump for particles within 25 hours TIS. Thereafter:
1 For 25 hours TIS, continue to inspect the MGB plugs for particles before each flight and perform the actions required by paragraphs g1i and ii of this AD.
2 Inspect the MGB filter and oil sump for particles at intervals not to exceed 25 hours TIS and perform the actions required by paragraphs g1i and ii of this AD.
B If any S is greater than 1 mm2, L is greater than 1.5 mm, or e is greater than 0.2
mm, perform a metallurgical analysis for any 16NCD13 particles, using a method in accordance with FAA-approved procedures.
C If there are any 16NCD13 particles, before further flight, replace the MGB with an airworthy MGB.
D If there are no 16NCD13 particles, inspect the MGB plugs for particles before further flight and inspect the MGB filter and oil sump for particles within 25 hours TIS.
Thereafter:
1 For 25 hours TIS, continue to inspect the MGB plugs for particles before each flight and perform the actions required by paragraphs g1i and ii of this AD.
2 Inspect the MGB filter and oil sump for particles at intervals not to exceed 25 hours TIS and perform the actions required by paragraphs g1i and ii of this AD.
ii If the total surface area of collected particles is greater than or equal to 3 mm2, before further flight, perform a metallurgical analysis for any 16NCD13 particles using a method in accordance with FAA-approved procedures.
A If there are any 16NCD13 particles, before further flight, replace the MGB with an airworthy MGB.
B If there are no 16NCD13 particles, inspect the MGB plugs for particles before further flight and inspect the MGB filter and oil sump for particles within 25 hours TIS.
Thereafter:

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1 For 25 hours TIS, continue to inspect the MGB plugs for particles before each flight and perform the actions required by paragraphs g1i and ii of this AD.
2 Inspect the MGB filter and oil sump for particles at intervals not to exceed 25 hours TIS and perform the actions required by paragraphs g1i and ii of this AD.
2 For helicopters with at least one Type Y planet gear assembly with an S/N listed in Appendix 4.A. of ASB EC15505A034 Rev 5 installed, within 25 hours TIS after the effective date of this AD, inspect the MGB
filter for particles. If there are any particles that consist of any scale, flake, splinter, or particle other than cotter pin fragments, pieces of lock wire, swarf, abrasion, or miscellaneous non-metallic waste, and any of the planet gears have accumulated more than 50 total hours TIS, before further flight, perform the actions required by paragraphs g1i and ii of this AD.
3 For helicopters with at least one Type Y planet gear assembly with an S/N listed in Appendix 4.A. of ASB EC15505A034 Rev 5 installed, within 50 hours TIS after the effective date of this AD, replace the MGB or as an alternative to replacing an affected MGB, replace the epicyclic reduction gear module in the affected MGB in accordance with paragraph 3.B.2. of the Accomplishment Instructions of Airbus Helicopters Service Bulletin SB No. EC15563016, Revision 4, dated July 26, 2018 SB EC15563016 Rev 4, except you are not required to contact Airbus Helicopters.
4 For helicopters without any Type Y
planet gear assembly installed but with at least one Type Z planet gear assembly with an S/N listed in Appendix 4.B. of ASB
EC15505A034 Rev 5 installed, within 50
hours TIS after the effective date of this AD, or before any gear accumulates 1,800 total hours TIS, whichever occurs later, replace the MGB or as an alternative to replacing an affected MGB, replace the epicyclic reduction gear module in the affected MGB in accordance with paragraph 3.B.2. of the Accomplishment Instructions of SB EC155
63016 Rev 4, except you are not required to contact Airbus Helicopters.
5 For helicopters with at least one Type Z planet gear assembly with an S/N listed in Appendix 4.B. of ASB EC15505A034 Rev 5
installed, inspect the MGB filter for particles within the compliance times specified in Figure 1 to paragraph g5 of this AD and inspect the oil sump for particles within the compliance times specified in Figure 2 to paragraph g5 of this AD, based on the total hours TIS accumulated by the Type Z planet gear with the most total hours TIS
accumulated since first installation in an MGB. If there are particles, before further flight, perform the actions required by paragraphs g1i and ii of this AD.

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